REVIEW
Two Particle States in an Asymmetric Box and the Elastic Scattering Phases
High Energy Physics - Lattice · Submitted 1 Apr 2004 · 18 references
Pith's verdict: A useful extension of Lüscher's formula to rectangular boxes, with a real gap in the D2 appendix that leaves Eq. (18) under-specified.
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Referee report
The paper
The paper claims
The paper derives determinant conditions that convert two-particle energy levels in a periodic rectangular box into continuum elastic scattering phases, generalizing Lüscher's cubic-box formula to $D_4$ and $D_2$ symmetry.
The reading
What carries the argument
The load-bearing device is the set of singular periodic solutions of the Helmholtz equation, built from $G_{ℓm}=Y_{ℓm}(∇)G$ with a periodic Green's function, and packaged into the modified zeta function $Z_{ℓm}(s,q^2;η_1,η_2)$ summed over the box momentum lattice $ñ=(n_1/η_1,n_2/η_2,n_3)$. Group theory then reduces the infinite matrix to blocks labelled by $D_4$ or $D_2$ irreducible representations, and the phase shifts enter through $U=(M+i)/(M-i)$ in the condition $det[e^{2iδ}-U]=0$. This is what turns a measured finite-box energy into a statement about continuum scattering.
Extended reading notes
Core claim
The central claim is that the exact two-particle energy eigenstates in a generic asymmetric rectangular box are still governed by a Lüscher-type determinant. For $D_4$ symmetry the $A_1^+$ sector gives a $4×4$ determinant involving $δ_0$, $δ_2$, and $δ_4$; for $D_2$ symmetry the $A^+$ sector gives a $6×6$ determinant because the reduced symmetry admits more independent basis polynomials. At low relative momentum $q$ both reduce to $δ_0(q)=Z_{00}(1,q^2;η_1,η_2)/(π^{3/2}η_1η_2 q)$, so the s-wave scattering length follows from $δE=-2πa_0/(η_1η_2μL^3)[1+c_1(η_1,η_2)(a_0/L)+c_2(η_1,η_2)(a_0/L)^2+⋯]$. The paper tabulates $c_1$ and $c_2$ for several aspect ratios and recovers the cubic-box values at $η_1=η_2=1$.
Load-bearing premise
The derivation is carried out in non-relativistic quantum mechanics and then asserted to carry over to relativistic massive field theory under the assumptions that the interaction range satisfies $R<L/2$ and that exponential finite-volume corrections can be neglected; that carry-over is inherited from Lüscher's framework rather than re-derived for the asymmetric topology.
Editorial extensions
If this is right
- For a $D_4$ box with $η_1=η_2≠1$, an $A_1^+$ two-particle energy level determines $δ_0$ through a $4×4$ determinant whose off-diagonal entries are the $d$- and $g$-wave admixtures.
- For a $D_2$ box with all sides unequal, the $A^+$ sector gives a $6×6$ determinant; at low $q$ it collapses to the same s-wave relation, $δ_0=Z_{00}/(π^{3/2}η_1η_2 q)$.
- The s-wave scattering length follows from the energy-shift formula with $c_1,c_2$ tabulated for aspect ratios such as $6:5:4$, $4:3:2$, and $2:1:1$; at $1:1:1$ the cubic-box values are recovered.
- Other symmetry sectors give access to higher partial waves: $E^+$, $B_1^+$, and $B_2^+$ for the $d$-wave in $D_4$, and $A_2^+$ for the $g$-wave.
- An asymmetric box provides more distinct low-lying momentum modes than a cubic box of the same shortest side, so non-zero relative momentum scattering may be reachable with smaller lattices.
Reading between the lines
- The sector-by-sector decomposition suggests a single asymmetric lattice could supply several partial-wave phase-shift points at once, since $E^+$, $B_1^+$, and $B_2^+$ levels probe the $d$-wave; the paper does not carry out that multi-sector extraction.
- The tabulated $c_1$ and $c_2$ vary substantially with aspect ratio, so a natural practical question is whether some aspect ratio minimizes finite-volume systematics for a fixed shortest side; the paper lists values but does not optimize.
- Because the relativistic carry-over is inherited rather than re-derived, a natural check is to repeat the derivation in a relativistic effective field theory or compare against a known-phase model in an asymmetric box.
- If exponential finite-volume corrections grow with anisotropy, the gain in low-momentum modes could be offset by harder-to-control systematics; quantifying that trade-off is left open.
Original abstract
The exact two-particle energy eigenstates in a generic asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained for both $D_4$ and $D_2$ symmetry. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by L\"uscher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these formulae are also discussed.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The exact two-particle energy eigenstates in a generic asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained for both $D_4$ and $D_2$ symmetry. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by L\"uscher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these formulae are also discussed.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The exact two-particle energy eigenstates in a generic asymmetric rectangular box with periodic boundary conditions in all three directions are studied. | contribution 1.00 | 0.90 | 0.07 | asserted 0.99 |
| s1 | Their relation with the elastic scattering phases of the two particles in the continuum are obtained for both $D_4$ and $D_2$ symmetry. | result 0.85 | 0.89 | 0.50 | asserted 1.00 |
| s2 | These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by L\"uscher before. | interpretation 0.76 | 0.37 | 0.20 | asserted 0.57 |
| s3 | In particular, the s-wave scattering length is related to the energy shift in the finite box. | result 0.96 | 0.72 | 0.21 | asserted 1.00 |
| s4 | Possible applications of these formulae are also discussed. | future work 0.80 | 0.54 | 0.04 | hedged possibility 0.75 |
What was examined, and what was not
- arXiv listing abstract v1
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Figures
Figures reproduced from arXiv:hep-lat/0404001 by the authors.
References
How the literature uses it
43 arXiv papers cite this in 70 sentences
Papers citing it · 51 sentences without a confident label
Builds on it 2 papers
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Elongated boxes have a different symmetry than cubic ones and different Lüscher formulas are required: for the zero-momentum case they were worked out in [ref] and in this paper we worked out the required one for states boosted along the elongated direction.
Rho resonance parameters from lattice QCD · Conclusions · 0.97
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Then, this formula was generalized to moving frames with center-of-mass momentum $P = (2π/L) k$ [ref] , [equation] where [equation] is the generalized zeta function.
Galilean invariance restoration on the lattice · Lüscher's formula · 0.80
Uses its method or tool 4 papers
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For energies below the inelastic threshold we use Lüscher's formula [ref] and the extensions to elongated boxes [ref] and boosted frames [ref] .
Pion scattering in the isospin I=2 channel from elongated lattices · Extracting physical quantities · 0.97
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To connect the two-hadron state energies determined from lattice QCD with the physical observables, i.e., the phase-shifts in the continuum, we use Lüscher's formula [ref] and its extensions to the elongated box [ref] and to states boosted along the elongated direction [ref] .
Extraction of isoscalar $\pi\pi$ phase-shifts from lattice QCD · Phase-shift formulas · 0.98
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Expanding Eq. ([ref]) by subsitituting Eqs. ([ref]) and ([ref]) follows: [equation] where $q= pL/2π$ is the dimensionless momentum, the term of $q δ$ can be determined from lattice calculations by Lüscher's method [ref] , and the zeta function $𝒵_00(s;q^2)$ is computed numerically [ref] .
First-Principles Determination of the Proton-Proton Fusion Matrix Element from Lattice QCD · Finite-Volume Analysis · 0.99
Compares with it 2 papers
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It is evident from the result, that it is consistent with all previous two-body finite volume results [ref] .
Two-particle multichannel systems in a finite volume with arbitrary spin · Conclusion · 0.87
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For the meson-meson scattering the formulas derived here for the states at rest agree with the one derived by in Ref. [ref] , while for the moving case they are mostly new.
Scattering phaseshift formulas for mesons and baryons in elongated boxes · Conclusion · 1.00
Cites it as background 8 papers
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It has been generalized in various ways over the years: to the boosted frames [ref] , to the case of asymmetric boxes [ref] , with twisted boundary conditions [ref] , to the case of particles with spin, e.g. to the case of two baryons [ref] and beyond the inelastic threshold [ref] , and even to three-particle case [ref] .
Generalized L\"uscher's Formula in Multichannel Baryon-Baryon Scattering · INTRODUCTION · 0.92
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The evaluation of these zeta functions is non-trivial but has been discussed in Refs. [ref] .
Higher order quantization conditions for two-body scattering with spin · Kinematics · 0.90
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For systems with PBCs, there has been a great deal of effort in reduction of these master equation for a wide variety of scenarios [ref] .
Two-particle multichannel systems in a finite volume with arbitrary spin · Two-particle multichannel systems with spin and PBCs · 0.87
Discussion
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